Power gauge for accurate measurement of load current

Abstract

According to one exemplary embodiment, a power gauge for accurately measuring current consumed by a load coupled to a power source includes a current sense resistor having a first terminal coupled to the power source and a second terminal coupled to the load. The power gauge further includes a first integrator configured to integrate a voltage at the first terminal of the current sense resistor during a time period and to output a first integrated voltage. The power gauge further includes a second integrator configured to integrate a voltage at the second terminal of the current sense resistor during the time period and to output a second integrated voltage. A difference between the first and second integrated voltages can be used to accurately determine the current consumed by the load during the time period.

1. A power gauge to accurately measure current consumed by a load coupled to a power source, said power gauge comprising:
 a current sense resistor having a first terminal coupled to said power source and a second terminal coupled to said load; 
 a first integrator configured to integrate a voltage at said first terminal of said current sense resistor during a time period and output a first integrated voltage; 
 a second integrator configured to integrate a voltage at said second terminal of said current sense resistor during said time period and output a second integrated voltage; 
 wherein an output voltage corresponding to an average of a difference between said voltage at said first terminal and said voltage at said second terminal determines said current consumed by said load during said time period. 
 
     
     
       2. The power gauge of  claim 1  further comprising a voltage differentiator configured to receive said first and second integrated voltages and to provide said output voltage. 
     
     
       3. The power gauge of  claim 2  further comprising a processing block configured to receive said output voltage from said voltage differentiator and to determine said current consumed by said load during said time period. 
     
     
       4. The power gauge of  claim 1 , wherein said load is a portable electronic device selected from the group consisting of a cell phone, a camera, a personal digital assistant, a laptop computer, a portable DVD, and an MP3 player. 
     
     
       5. The power gauge of  claim 2 , wherein said first integrated voltage is received at a non-inverting input of said voltage differentiator and said second integrated voltage is received at an inverting input of said voltage differentiator. 
     
     
       6. The power gauge of  claim 1 , wherein said first integrated voltage is linearly proportional to said voltage at said first terminal of said current sense resistor and said second integrated voltage is linearly proportional to said voltage at said second terminal of said current sense resistor. 
     
     
       7. The power gauge of  claim 1 , wherein said power source is a battery. 
     
     
       8. The power gauge of  claim 1 , wherein said first integrator continuously samples said voltage at said first terminal of said current sense resistor during said time period and said second integrator continuously samples said voltage at said second terminal of said current sense resistor during said time period. 
     
     
       9. The power gauge of  claim 1 , wherein said power gauge is fabricated on a semiconductor die. 
     
     
       10. The power gauge of  claim 9 , wherein said semiconductor die includes a circuit selected from the group consisting of a memory array, a processor, a multi-media module, and a transceiver. 
     
     
       11. A power gauge comprising:
 a first integrator configured to integrate a voltage at a first terminal of a current sense resistor and output a first integrated voltage, said first terminal of said current sense resistor coupled to a power source; 
 a second integrator configured to integrate a voltage at a second terminal of said current sense resistor and output a second integrated voltage, said second terminal of said current sense resistor coupled to a load; 
 a voltage differentiator configured to receive said first and second integrated voltages and to provide an output voltage corresponding to an average of a difference between said voltage at said first terminal and said voltage at said second terminal; 
 wherein said output voltage corresponds to an average current consumed by said load. 
 
     
     
       12. The power gauge of  claim 11  further comprising a processing block configured to receive said output voltage from said voltage differentiator and to determine said average current consumed by said load. 
     
     
       13. The power gauge of  claim 11 , wherein said load draws a constant current through said current sense resistor. 
     
     
       14. The power gauge of  claim 11 , wherein said load draws a variable current through said current sense resistor. 
     
     
       15. The power gauge of  claim 11 , wherein said load is a portable electronic device selected from the group consisting of a cell phone, a camera, a personal digital assistant, a laptop computer, a portable DVD, and an MP3 player. 
     
     
       16. The power gauge of  claim 11 , wherein said first integrated voltage is linearly proportional to said voltage at said first terminal of said current sense resistor and said second integrated voltage is linearly proportional to said voltage at said second terminal of said current sense resistor. 
     
     
       17. The power gauge of  claim 11 , wherein said first and second integrators each includes a pair of transistors coupled together in a current mirror configuration. 
     
     
       18. The power gauge of  claim 11 , wherein said power source is a battery. 
     
     
       19. The power gauge of  claim 11 , wherein said power gauge is fabricated on a semiconductor die. 
     
     
       20. The power gauge of  claim 19 , wherein said semiconductor die includes a circuit selected from the group consisting of a memory array, a processor, a multi-media module, and a transceiver.